POS0125 EXTRA-ARTICULAR FINDINGS WITH FDG-PET/CT IN RHEUMATOID ARTHRITIS PATIENTS: MORE HARM THAN BENEFIT.
Authors: E. Ulijn, A. Den Broeder, N. Boers, M. Gotthardt, C. Bouman, R.B.M. Landewé, N. Den Broeder, N. Van Herwaarden
Journal: Annals of the Rheumatic Diseases (2022)

<h3>Background</h3> Whole-body Positron Emission Tomography with CT-scanning using fluorine-18 fluorodeoxyglucose (18F-FDG) is occasionally used in Rheumatoid Arthritis (RA) patients. Reasons to use FDG-PET/CT-scans are to diagnose arthritis or guide decisions on systemic therapy, as FDG uptake in affected joints may reflect disease activity [1]. FDG-PET/CT might also detect malignancies, but the frequency of incidental findings and the proportion of relevant malignant disease that could be missed are currently unknown. <h3>Objectives</h3> To study the malignancy screening performance of whole-body FDG-PET/CT in longstanding RA patients with low disease activity. <h3>Methods</h3> FDG-PET/CT-scanning was done in the intervention arm of the Dose REduction Strategy of Subcutaneous TNF-inhibitors (DRESS) study, a randomized controlled trial on dose-tapering of biological Disease Modifying Anti-Rheumatic Drugs (bDMARDs) [3]. Baseline and if applicable follow up whole-body FDG-PET/CT-scans were performed in consenting patients in the tapering arm to assess predictive value of subclinical PET-arthritis for risk of flaring [4]. The scans were also read by experienced nuclear medicine specialists immediately after they were performed for any unexpected extra-articular finding, conform routine clinical care. The reference standard was clinical diagnosis of malignancy during the 3 year follow-up. Prevalence of extra-articular abnormalities, follow-up, and received treatments were summarized post-hoc. <h3>Results</h3> 121 scans were made in 79 patients. Extra-articular abnormalities were found in 59/121 (48.8%) scans (Table 1) in 45/79 (57%) patients. Follow-up action occurred in 21 (26.6%) patients, consisting of referral to a specialist or reassessing and/or scheduling diagnostics directly by the treating rheumatologist. In 5 (6.3%) patients, the rheumatologist followed-up. In 17 (21.5%) patients a consultation with a different specialist was scheduled. In five patients surgical/invasive intervention took place. In one patient a hemi-thyroidectomy was performed revealing a follicular adenoma. This resection was complicated by persistent recurrent laryngeal nerve paresis and hoarseness. In a second, an intra-uterine myomectomy took place. In a third, a colonoscopy was performe revealing two low-grade adenomas. In a fourth a benign cyst in the neck was extracted. A fifth patient underwent spinal marginal myotomy which turned out to be a benign schwannoma. Nine patients (7.4%) were suspected of malignancy, none turned out to be malignant. Six clinical malignancies (bladder, penile, lymphoma, 2x melanoma and prostate) that developed during follow-up were all negative on baseline FDG-PET/CT. The malignancies were diagnosed after an interval of between 5 and 34 months (mean 13 months). <h3>Conclusion</h3> Whole-body FDG-PET/CT-scanning for arthritis imaging in RA patients results in frequent incidental extra-articular findings, while some who apparently had normal scans developed malignancies. <h3>References</h3> [1]Mandl P. et al. RMD open 2019;5:e000950. [2]Van Herwaarden N. et al. BMJ 2015;350:1–8. doi:10.1136/bmj.h1389 [3]Bouman C.A.M et al. <i>Rheumatology</i> 2021. <h3>Disclosure of Interests</h3> None declared